Steps that I have done to troubleshoot including:
- unplug & plug all the HDDs.
- relocate all SATA cables
- relocate the RAM to another slot
- change power cord
- check CPU temperature
Before power up the server, reading the manual of motherboard I realize the Execute Disable Bit seems not officially supported on Ubuntu. I then disable the function.
Everything seems working fine afterwards. I have not tested whether it is the BIOS which caused the problem or the Execute Disable Bit create the problem, but if you do encounter the same problem like I did, try disable it. May save your day. =)